Diabetes mellitus is a disease derived from multiple causative factors and characterized by elevated levels of plasma glucose (hyperglycemia) in the fasting state or after administration of glucose during an oral glucose tolerance test. There are two generally recognized forms of diabetes. In Type 1 diabetes, or insulin-dependent diabetes mellitus (IDDM), patients produce little or no insulin, the hormone which regulates glucose utilization. In Type 2 diabetes, or noninsulin-dependent diabetes mellitus (NIDDM), insulin is still produced in the body, however patients with Type 2 diabetes have a resistance to the effects of insulin in stimulating glucose and lipid metabolism in the insulin-sensitive muscle, liver and adipose tissues. These patients often have normal levels of insulin, and may have hyperinsulinemia (elevated plasma insulin levels), as they compensate for the reduced effectiveness of insulin by secreting increased amounts of insulin. This lack of responsiveness to insulin results in insufficient insulin-mediated activation of uptake, oxidation and storage of glucose in muscle, and inadequate insulin-mediated repression of lipolysis in adipose tissue and of glucose production and secretion in the liver.
Persistent or uncontrolled hyperglycemia that occurs with diabetes is associated with increased and premature morbidity and mortality. Abnormal glucose homeostasis is associated both directly and indirectly with obesity, hypertension, and alterations of the lipid, lipoprotein and apolipoprotein metabolism, as well as other metabolic and hemodynamic disease. Patients with Type 2 diabetes mellitus have a significantly increased risk of macrovascular and microvascular complications, including atherosclerosis, coronary heart disease, stroke, peripheral vascular disease, hypertension, nephropathy, neuropathy, and retinopathy. Therefore, therapeutic control of glucose homeostasis, lipid metabolism, obesity, and hypertension are critically important in the clinical management and treatment of diabetes mellitus.
Patients who have insulin resistance often have Metabolic Syndrome, which is characterized as having three or more symptoms selected from the following group of five symptoms: (1) abdominal obesity; (2) hypertriglyceridemia; (3) low high-density lipoprotein cholesterol (HDL); (4) high blood pressure; and (5) elevated fasting glucose, which may be in the range characteristic of Type 2 diabetes if the patient is also diabetic (as defined in the Third Report of the National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III, or ATP III), National Institutes of Health, 2001, NIH Publication No. 01-3670). Patients with Metabolic Syndrome have an increased risk of developing the macrovascular and microvascular complications that occur with Type 2 diabetes, such as atherosclerosis and coronary heart disease.
There are several available treatments for Type 2 diabetes. Physical exercise and a reduction in dietary intake of calories often dramatically improve the diabetic condition and are the usual recommended first-line treatment of Type 2 diabetes and of pre-diabetic conditions associated with insulin resistance, however compliance with this treatment is generally very poor. Pharmacologic treatments for diabetes have largely focused on three areas of pathophysiology: (1) hepatic glucose production (biguanides, such as phenformin and metformin), (2) insulin resistance (PPAR agonists, such as rosiglitazone, troglitazone, engliazone, balaglitazone, MCC-555, netoglitazone, T-131, LY-300512, LY-818 and pioglitazone), (3) insulin secretion (sulfonylureas, such as tolbutamide, glipizide and glimipiride); (4) incretin hormone mimetics (GLP-1 derivatives and analogs, such as exenatide, liraglutide, dulaglutide, semaglutide, lixisenatide, albiglutide and taspoglutide); and (5) inhibitors of incretin hormone degradation (DPP-4 inhibitors, such as sitagliptin, alogliptin, vildagliptin, linagliptin, denagliptin and saxagliptin).
The biguanides are a class of drugs that are widely used to treat Type 2 diabetes. The two best known biguanides, phenformin and metformin, cause some correction of hyperglycemia, but can induce lactic acidosis and nausea/diarrhea. Metformin has a lower risk of side effects than phenformin and is widely prescribed for the treatment of Type 2 diabetes.
The glitazones (e.g. 5-benzylthiazolidine-2,4-diones) can ameliorate hyperglycemia and other symptoms of Type 2 diabetes. Glitazones, such as rosiglitazone and pioglitazone, are peroxisome proliferator activated receptor (PPAR) gamma subtype agonists, and are modestly effective in reducing plasma glucose and HemoglobinA1C. The currently marketed compounds do not greatly improve lipid metabolism and may actually have a negative effect on the lipid profile.
Another widely used drug treatment involves the administration of insulin secretagogues, such as the sulfonylureas (e.g. tolbutamide, glipizide, and glimepiride). Sulfonylureas and related insulin secretagogues act by blocking the ATP-dependent K+ channel in β-cells, which causes depolarization of the cell and the opening of the voltage-dependent Ca2+ channels with stimulation of insulin release. This mechanism is non-glucose dependent, and hence insulin secretion can occur regardless of the ambient glucose levels. This can cause insulin secretion even if the glucose level is low, resulting in hypoglycemia, which can be fatal in severe cases. The administration of insulin secretagogues must therefore be carefully controlled.
Dipeptidyl peptidase IV (DPP-4) inhibitors (e.g., sitagliptin, alogliptin, vildagliptin, linagliptin, denagliptin and saxagliptin) provide a route to increase insulin secretion in response to food consumption.
Studies with DPP-4(−/−)-deficient mice and clinical trials with DPP-4 inhibitors indicate that DPP-4 inhibition increases the steady state concentrations of GLP-1 and GIP, resulting in improved glucose tolerance. As a result DPP-4 inhibitors have utility in the treatment of Type 2 diabetes, as well as numerous conditions that often accompany Type 2 diabetes, including Metabolic Syndrome, reactive hypoglycemia, and diabetic dyslipidemia.
There has been a renewed focus on pancreatic islet-based insulin secretion that is controlled by glucose-dependent insulin secretion. This approach has the potential for stabilization and restoration of β-cell function. In this regard, several orphan G-protein coupled receptors (GPCR's) have recently been identified that are preferentially expressed in the β-cell and that are implicated in glucose stimulated insulin secretion (GSIS). GPR40 is a cell-surface GPCR that is highly expressed in human (and rodent) islets as well as in insulin-secreting cell lines. Several naturally-occurring medium to long-chain fatty acids (FA's) as well as synthetic compounds, including several members of the thiazolidinedione class of PPARγ agonists, have recently been identified as ligands for GPR40 [Itoh, Y. et al., Nature, 422: 173 (2003); Briscoe, C. P. et al., J. Biol. Chem., 278: 11303 (2003); Kotarsky, K. et al., Biochem. Biophys. Res. Comm., 301: 406 (2003)]. Under hyperglycemic conditions, GPR40 agonists are capable of augmenting the release of insulin from islet cells. The specificity of this response is suggested by results showing that the inhibition of GPR40 activity by siRNA attenuates FA-induced amplification of GSIS. These findings indicate that, in addition to the intracellular generation of lipid-derivatives of FA's that are thought to promote insulin release, FA's (and other synthetic GPR40 agonists) may also act as extracellular ligands that bind to GPR40 in mediating FA-induced insulin secretion. There are several potential advantages of GPR40 as a potential target for the treatment of Type 2 diabetes. First, since GPR40-mediated insulin secretion is glucose dependent, there is little or no risk of hypoglycemia. Second, the limited tissue distribution of GPR40 (mainly in islets) suggests that there would be less chance for side effects associated with GPR40 activity in other tissues. Third, GPR40 agonists that are active in the islets may have the potential to restore or preserve islet function. This would be highly advantageous, because long term diabetes therapy often leads to the gradual diminution of islet activity, so that after extended periods of treatment, it is often necessary to treat Type 2 diabetic patients with daily insulin injections. By restoring or preserving islet function, GPR40 agonists may delay or prevent the diminution and loss of islet function in a Type 2 diabetic patient.
Compounds that are agonists of G-protein-coupled receptor 40 (GPR40) may be useful to treat type 2 diabetes mellitus, obesity, hypertension, dyslipidemia, cancer, and metabolic syndrome, as well as cardiovascular diseases, such as myocardial infarction and stroke, by improving glucose and lipid metabolism and by reducing body weight.
There is a need for potent GPR40 agonists that have pharmacokinetic and pharmacodynamic properties suitable for use as human pharmaceuticals.
G-protein-coupled receptor 40 (GPR40) agonists are disclosed in: WO 2004/022551, WO 2004/041266, WO 2005/051373, WO 2005/051890, WO 2005/063729, WO 2005/086661, WO 2005/087710, WO 2006/038738, WO 2006/083612, WO 2006/083781, WO 2006/127503, WO 2007/033002, WO 2007/101368, WO 2007/106469, WO 2007/123225, WO 2007/131619, WO 2007/131620, WO 2007/131621, WO 2007/131622, WO 2007/136572, WO 2007/136573, WO 2007/213364, WO 2008/001931, WO 2008/030520, WO 2008/030618, WO 2008/054674, WO 2008/054675, WO 2008/058237; WO 2008/066097, WO 2008/130514, WO 2008/139987, WO 2009/038204, WO 2009/039942, WO 2009/039943, WO 2009/048527, WO 2009/054390, WO 2009/054423, WO 2009/054479, WO 2009/058237, WO 2009/111056, WO 2010/025424, WO 2010/045258, WO 2010/085522, WO 2010/085525, WO 2010/085528, WO 2010/085528, WO 2010/091176, WO 2010/091176, WO 2010/123016, WO 2010/123017, WO 2010/143733, WO 2011/052756, WO 2011/066183, WO 2012/011125, WO 2012/030566, WO 2012/046869, WO 2012/072691, WO 2013/025424, WO 2013/104267, US 2007/0265332, US 2013/0252937, WO 2013/122028, WO 2013/122029, WO 2013/128378, US2013/0172248, CN 2013/103012343A, CN 2013/103145663A, CN 2012/10300982.7, CN 103030646 and GB 2498976.
GPR40 agonists are also disclosed in Walsh et al., Bioorganic & Medicinal Chemistry Letters (2011), 21(11), 3390-3394; Zhou et al., Bioorganic & Medicinal Chemistry Letters (2010), 20(3), 1298-1301; Tan et al., Diabetes (2008), 57(8), 2211-2219; Houze et al., Bioorganic & Medicinal Chemistry Letters (2012), 22(2), 1267-1270; Brown et al., ACS Medicinal Chemistry Letters (2012), 3(9), 726-730; Lin et al., PloS One (2011), 6(11), e27270; Lou et al., PloS One (2012), 7(10), e46300; Lin et al., Molecular Pharmacology (2012), 82(5), 843-859; Yang, Lihu, Abstracts of Papers, 239th ACS Meeting, San Francisco, Calif., USA Mar. 21-25, 2010 MEDI-313; and Houze et al., Abstracts of Papers, 243rd ACS National Meeting & Exposition, San Diego, Calif., USA Mar. 25-29, 2012, MEDI-265.